The invention relates to a planetary transmission with a continuously variable belt drive.
An example of prior art relating to the planetary gear portion of the invention is described in German Pat. No. 11 26 212. The carrier assembly of the planetary gearing of that reference comprises two sets of planet pinions that mesh with one another and form the input member. The sun gear forms the output member and the ring gear forms the reaction member. Reverse drive can be effected by locking the ring gear by means of a friction disc brake. Forward drive can be effected by connecting the carrier assembly to the sun gear by means of a friction disc clutch. The friction disc clutch and brake can be actuated hydraulically by means of piston-cylinder units.
The axial structural length of the transmission of the prior art reference is too long for many applications and the ring gear is not guided and supported against axial movement.
Another example of related prior art is shown in German Pat. No. 32 41 789. That reference describes a transmission having friction disc clutches constructed in the form of multiple-disc assemblies. The forward drive clutch, which connects the planetary carrier to the sun gear, must be supplied with pressure fluid for the associated piston-cylinder unit in a complicated flow path through radial bores in different hollow shafts. Here too the structural length of the transmission is undesirably long and the supply of lubricating oil to the planetary gearing is difficult.
A third example of related prior art is described in German Patent Application P No. 35 38 884.6, which describes a so-called torque sensor disposed in the region of the forward drive clutch. As a result, an additional sleeve member, by way of which the pressure fluid for the forward drive clutch is supplied by way of radial bores, is added to the hollow shafts already present. In this case axial cavities used for distributing the pressure fluid must be sealed off by corresponding sealing rings. These adversely affect the sensitivity of the torque sensor on account of their friction.